JP3095975B2 - Optical switching network - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical switching network for selectively connecting an optical signal from one line to another line.

[0002]

2. Description of the Related Art Optical switching technology for selectively connecting an optical signal transmitted from an optical fiber from one line to another line while keeping the light, has been actively studied. As one of the core devices of the optical switching, there is an optical switching network (sometimes called an optical matrix switch). In this case, connection of an optical signal from one line to another line is electrically performed.

The optical switching network can be roughly classified into a completely non-blocking type, a rearrangement non-blocking type, and a blocking type. A typical matrix configuration of these types is
Reference 1: "S. Hinton, An Introduction to Photonic
Switching Fabrics, PLENUM, pp. 83-113, 1993 ". For example, there are a tree type and a crossbar type as a completely non-occluding type, a Benes type as a rearrangement non-occluding type, and a Banyan type as a closed type.

[0004]

Generally, an optical switching network is considered to be of a non-blocking type, particularly a completely non-blocking type, rather than a blocking type, in consideration of the functionality, that is, the degree of freedom in connecting lines. FIG. 6 shows the completely non-occluding type described above,
1 shows typical matrix configurations of a rearrangement non-blocking type and a blocking type. FIG. 6A shows a tree-type optical switching network having four input ports and four output ports, and FIG. 6B shows a cross-type optical switching network having four input ports and four output ports. FIG. 6C shows a Barnes type optical switching network having four input ports and four output ports, and FIG.
(D) shows a banyan-type optical switching network having four input ports and four output ports. 6 (A) to 6 (D), the unit optical switches 26 are indicated by hatching. However, reference numeral 26
Is attached only to some of the unit optical switches, and the waveguides connect between the unit optical switches 26.

In forming an optical switching network, it is necessary to consider not only the functionality but also the crosstalk characteristics of the optical switching network and the length of the optical switching network.

FIG. 7 shows a result obtained by calculating a crosstalk characteristic SXR (worst worst-case Stokes value) of the optical switching network with respect to the number of input ports. The vertical axis indicates the crosstalk characteristic SXR of the optical switching network. In FIG. 7, a curve a represents a crossbar type, a curve b represents a tree type, a curve c represents a Benes type, and a curve d represents a crosstalk characteristic of a banyan type optical switching network. The result if equal. In this case, the crosstalk characteristic SXR for the crossbar type
Is calculated using the equation (3.3.6) in the literature 1, that is, the following equation (1). The calculation of the crosstalk characteristic SXR for the tree type is performed using the equation (3.3.10) in the literature 1. )formula,
That is, using the following equation (2), the calculation of the crosstalk characteristic SXR with respect to the Benes type requires the calculation of (3.3.
Expression (15), that is, the following expression (3) was used, and the following expression (4) was used to calculate the crosstalk characteristic SXR for the Banyan type. In the equations (1) to (4), N indicates the number of input ports, and _Xc indicates a crosstalk characteristic with respect to the unit optical switch. L in the equation (1) indicates a crosstalk characteristic at the intersection of the waveguides. Then, X _c = −25 dB, L
= 0 and N was calculated in the range of 2 to 128.

SXR = −X _c −10 log [(1-10 ^{(1-N) L / 10} ) / (10 ^{L / 10} −1)] (1) SXR = −10 log [log ₂ N] −2X _c ( _{2) SXR = -10log [2log 2} N -1] -X c (3) SXR = -10log as can be understood from _{[2log 2 2N -1] -X c} (4) FIG. 7, when the number of input ports is equal ,
The tree-type SXR is about twice or more than the banyan-type, Benes-type, and crossbar-type, and is best, and the SXR deteriorates in the order of the banyan-type, Benes-type, and crossbar-type.

When the length of the optical switching network is considered, the tree type, Benes type and Banyan type are more advantageous than the crossbar type. This is because, when the number of input ports and the number of output ports are equal, the crossbar type increases the number of unit optical switches in proportion to the number of input ports, whereas the tree type, Benes type, and banyan type have input ports. This is because the number of stages of the unit optical switch increases in proportion to the logarithm of the number of ports (in short, in proportion to log ₂ (the number of input ports)).

FIG. 8 shows the result obtained by calculating the length of the optical switching network with respect to the number of input ports. The number of input ports is plotted on the horizontal axis (logarithmic scale with a base of 2), and the vertical axis (common logarithmic scale). ) Shows the length of the optical switching network. In FIG. 8, a curve e shows a crossbar type, a curve f shows a tree type, a curve g shows a Benes type, and a curve h shows a banyan type optical switching network, and the results when the number of input ports and the number of output ports are equal, respectively. It is. in this case,
Substrate material: LiNbO ₃ , unit optical switch length: 6 m
m, the radius of curvature of the waveguide is assumed to be 40 mm, and the minimum intersection angle of the waveguide is assumed to be 6 °. Further, the interval between the unit optical switches is set to 50 μm for the crossbar type, and 100 μm for the others.
m.

As can be understood from FIG. 8, when the number of input ports is the same, the length of the optical switching network is the shortest in the Banyan type, and becomes longer in the order of Benes type, tree type, and crossbar type. In any case, as the number of input ports increases, the length of the optical switching network increases. Therefore, when forming an optical switching network, the number of input ports is limited by the size of the substrate. For example, when an optical switching network is formed under the same conditions as in FIG. 8 with the substrate size being 100 mm, the maximum number of input ports when the number of input ports is represented by 2 ⁿ (n is an integer of 2 or more) is as follows: The banyan type is 64, the Benes type is 16, the tree type is 8, and the crossbar type is 4.

As described above, the tree type, the banyan type,
Among the Benes type and the crossbar type, the crosstalk characteristic SXR is the best in the tree type. However, when the number of input ports is 100 or more, the length of the optical switching network becomes long, and it becomes difficult to form the optical switching network. Therefore, attention was paid to the banyan type having the shortest optical switching network and the best crosstalk characteristic among the banyan type, Benes type, and crossbar type other than the tree type. However, since the banyan type is a closed type, the functionality is insufficient compared with a non-blocking type optical switching network. Further, when the number of input ports becomes 100 or more, the crosstalk characteristic of the banyan-type optical switching network becomes 20
dB or less, and the deterioration of the crosstalk characteristic cannot be ignored. Here, in order to maintain the crosstalk characteristics even when the number of input ports is 100 or more, it is necessary to improve the crosstalk characteristics with respect to the unit optical switch. , -25 dB or more.

Therefore, even if the number of ports is increased, there is no need to worry about the difficulty of formation due to the length, and there has been a demand for an optical switching network which is excellent in functionality and crosstalk characteristics.

[0013]

Therefore, according to the switching network of the present invention, there are N input ports and N output ports formed by a plurality of waveguides and a plurality of unit optical switches. An input stage configured by arranging N / 4 banyan-type optical switching units (hereinafter may be abbreviated as an N-input / N-output banyan-type optical switching unit or an N-input / N-output unit); A unit having N input ports and N output ports formed of a waveguide and a plurality of unit optical switches is denoted by N.
/ 4 output stages and an input stage connected to the output stage. Here, N is 2 ^a (a is an integer of 3 or more).

Each of the units at the input stage has a portion which operates as four 1-input N / 4-output branch optical switches from the input port side to the output port side of the individual unit at the input stage. Thus, among the N input ports of the individual units in the input stage, four input ports connected to different unit optical switches are selected as input ports of the optical switching network. For this reason, each N-input N-output banyan optical switching unit in the input stage apparently branches four 1-input N / 4 outputs from the input port side to the output port side of the optical switching network. A part that operates as an optical switch and N / 4 4
It can be regarded as a configuration in which a part operating as an input four-output banyan optical switch is connected.

Similarly, each unit in the output stage has a portion that operates as four 1-input N / 4 output branch optical switches from the output port side to the input port side of each unit in the output stage. From among the N output ports of the individual units in the output stage, four output ports connected to different unit optical switches are selected as output ports of the optical switching network. For this reason, each of the N-input N-output banyan optical switching units of the output stage apparently branches four 1-input N / 4 outputs from the output port side to the input port side of the optical switching network. A part that operates as an optical switch and N / 4 4
It can be regarded as a configuration in which a part operating as an input four-output banyan optical switch is connected.

Further, according to the optical switching network of the present invention, each of the N / 4 units of the input stage is connected to each of the N / 4 units of the output stage. Is connected to four output ports connected to two adjacent unit optical switches among N output ports of the unit of the input stage, and N input ports of the unit of the output stage. Among them, four input ports connected to two adjacent unit optical switches are connected via a path bundle composed of two parallel paths and two cross paths.

In this case, any one path bundle, four output ports of the input-stage banyan optical switching unit connected by the path bundle, and four output ports of the output-stage banyan optical switching unit. A total of four unit optical switches connected to the input ports, a total of eight waveguides connected to the four unit optical switches, a total of four unit optical switches connected to the eight waveguides, and the four unit optical switches A portion composed of a total of eight waveguides connected to one unit optical switch operates as a non-blocking type 4-input / 4-output optical switch in a broad sense. That is, two 4-input 4-output banyan-type optical switches (one each for the input stage and the output stage) connected to any one path bundle.
Each is provided. ) Operates as a non-blocking four-input four-output optical switch in a broad sense.

With the above configuration, the optical switching network of the present invention apparently has N 1-input N / 4-output branch light from the input port side to the output port side of the optical switching network. The part that operates as a switch, N ²
It can be regarded as a configuration in which / 16 pieces of parts operating as non-blocking type 4-input / 4-output optical switches in a broad sense and N pieces of parts operating as N / 4-input / 1-output branch optical switches are connected. The crosstalk of the optical switching network of the present invention is basically a non-blocking four-input four-input
It occurs only in the part that operates as an output optical switch.
Since the light transmitted through the four-input four-output optical switch passes through the four unit optical switches, the crosstalk of the optical switching network according to the present invention is only 6 dB worse than the unit optical switch.

When forming the optical switching network of the present invention, first, a banyan optical switching unit is formed independently, and thereafter, a plurality of banyan optical switching units are used and connected as described above. Therefore, it is only necessary to form a banyan optical switching unit on the same substrate. Therefore, it is possible to reduce the adverse effect that the formation of the optical switching network becomes difficult because the length of the optical switching network becomes longer. Further, when the optical switching network of the present invention is formed on the same substrate, the length of the optical switching network is about the sum of the input stage and the output stage, that is, the length of the banyan optical switching unit constituting the input stage. , About the sum of the length of the banyan optical switching unit constituting the output stage. Since the length of the banyan optical switching network is originally short, even in the case of the optical switching network of the present invention in which the two stages (input stage and output stage) are combined, the length of the optical switching network can be suppressed to be short. it is conceivable that.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the switching network according to the present invention will be described below with reference to the drawings. In these drawings, each component merely schematically shows the shape, size, and positional relationship of each component to the extent that the present invention can be understood. In each of the drawings used for the description, the same components are denoted by the same reference numerals. In some drawings, reference numerals may be partially omitted.

In the following description, the basic configuration of the optical switching network of the present invention will be described to facilitate understanding of the present invention, and then specific examples will be described in the first and second embodiments.

1. Basic Configuration FIG. 1 is a schematic diagram for explaining a basic configuration of an optical switching network according to the present invention. As shown in FIG. 1, the optical switching network 50 of the present invention has N input ports and N input ports.
The banyan-type optical switching unit having a plurality of output ports (hereinafter sometimes referred to as a unit banyan-type optical switching network) 16a is N / 4 (where N is 2 ^a (a is an integer of 3 or more)). ) Input stage 12 and the banyan optical switching unit 16b
/ 4 output stages 14.
In this case, each banyan optical switching unit 1
6a and 16b are formed on different substrates (not shown). Then, any one banyan optical switching unit 16a of the input stage 12 and any one banyan optical switching unit 16b of the output stage 14
Are schematically shown connected, for example, via an optical fiber 18. Each banyan optical switching unit 16a, 16b having N input ports and N output ports includes a plurality of waveguides (including input ports and output ports) and a plurality of unit optical switches. However, in FIG. 1, they are collectively represented by a square. However, the optical switching network 5
Only waveguides used as zero input port 20 and output port 22 are shown by solid lines outside the square. That is, each banyan optical switching unit 16a of the input stage 12 has N input ports, but only four input ports are used when operating the optical switching network 50 for the purposes of the present invention. Not
The input port 20 used is shown in FIG. 1 and other input ports are omitted. Similarly, each banyan-type optical switching unit 16b of output stage 14 has N output ports, but only four output ports are required when operating optical switching network 50 for the purposes of the present invention. Since it is not used, the output port 22 to be used is shown in FIG. 1 and other output ports are omitted.

FIG. 2 is a schematic diagram for explaining the configuration of the banyan-type optical switching unit 16a constituting the input stage 12. As shown in FIG. 2, the banyan optical switching unit 16a formed on the substrate 10 includes a front stage 16ax and a rear stage 16a connected to the front stage 16ax.
y. The former stage 16ax operates as a branch switch formed by combining the waveguide and the unit optical switch 26. Which combination of the unit optical switches 26 (indicated by white circles in the figure) constitutes this branch switch depends on which input port of the input ports of the banyan optical switching unit 16a is input to the switching network 50. It depends on whether it is used as a port. In the present invention, since four input ports are used as input ports of the switching network 50, the former stage 16a
x operates as four 1-input N / 4-output branch switches. On the other hand, the latter stage 16ay operates as N / 4 4-input 4-output banyan optical switches. First stage 16ax
Operates as four 1-input N / 4-output branch switches. Therefore, of the N input ports of the banyan optical switching unit 16a constituting the input stage 12, four inputs connected to different unit optical switches are provided. The port is used as the input port 20 of the optical switching network 50. Also, the subsequent stage 16ay is a 4-input 4-output banyan optical switch N /
In order to operate as four, the N output ports of the banyan optical switching unit 16a constituting the input stage 12 are used as output ports 24 for connection to the individual banyan optical switching units 16b constituting the output stage 14. .

FIG. 2 shows only a part of the plurality of waveguides and the plurality of unit optical switches 26 forming the banyan optical switching unit 16a. In FIG. 2, the unit optical switches 26 forming the former stage 16ax are indicated by white circles as described above.
The unit optical switches 26 forming the latter stage 16ay are indicated by hatching in circles (the same in the following embodiments). The configuration of the banyan-type optical switching unit 16a constituting the input stage 12 and the output stage 1
4 constitutes a banyan-type optical switching unit 16b
The configuration is the same. Therefore, when the banyan optical switching unit 16a shown in FIG. 2 is used as the banyan optical switching unit 16b constituting the output stage 14, the input port 2 of the optical switching network 50
From the 0 side to the output port 22 side, there are N / 4 4-input / 4-output banyan-type optical switches and four 1-input N / 4-output branch switches. Just place them. In this case, of the N output ports of the banyan optical switching unit 16b constituting the output stage 14, four output ports connected to different unit optical switches are used as the output ports 22 of the optical switching network 50, and N input ports of the banyan optical switching unit 16b constituting the stage 14 are used as input ports for connection with the individual banyan optical switching units 16a constituting the input stage 12.

2. First Embodiment FIG. 3 is a schematic diagram illustrating an optical switching network according to a first embodiment. The switching network according to the first embodiment is a switching network in which N is set to 8. That is, FIG.
FIG. 1 shows an optical switching network 100 including an input stage 12 and an output stage 14 which are configured by arranging two banyan-type optical switching units, and in which the input stage 12 and the output stage 14 are connected. I have.

Each banyan-type optical switching unit is formed of a plurality of waveguides (including an input port and an output port) and a plurality of unit optical switches, and has eight input ports and eight output ports. In this case, each banyan-type optical switching unit is formed on a different substrate 10. As the substrate 10,
For example, a lithium niobate (LiNbO ₃ ) substrate is used. The waveguide can be formed in the substrate or on the substrate by a well-known waveguide fabrication technique according to the constituent material of the substrate. In addition, a known optical switch can also be formed by a known optical switch manufacturing technique according to the constituent material of the substrate. Note that in Figure 3, of the Banyan optical switching unit 16a _1, 16a ₂ of having input ports of the input stage 12, eight input ports 20 ₁ to 20 combined is used as an input port of the optical switching network 100 ₈ out of the output ports of the banyan optical switching units 16b ₁ and 16b ₂ of the output stage 14, only _eight output ports 22 _{1 to} 22 ₈ used as the output ports of the optical switching network 100 are combined. Is shown.
In FIG. 3, reference numerals 24 _{1 to} 24 ₁₆ denote input stage 12 and output stage 1.
4 and a Banyan optical switching unit 16a _1, 16a ₂ connected output port with the input stage 12 used for connection, the 28 _{1-28 16} input stage 12 and output stage 1
4 is a connection input port of the banyan-type optical switching units 16b ₁ and 16b ₂ of the output stage 14 used for connection to the input stage 4.

Further, the input Banyan optical switching unit 16a ₁ of the stage 12, and when focusing on Banyan optical switching units 16b ₁ of the output stage 14, input stage 12 Banyan optical switching unit 16a ₁ 8 amino with the Of the output ports, four connection output ports 24 ₁ to 24 ₁ connected to two adjacent unit optical switches.
24 ₄ and four connection input ports 28 _{1 to} 28 ₄ connected to two adjacent unit optical switches among the eight input ports of the banyan optical switching unit 16b ₁ of the output stage 14. They are connected via a path bundle consisting of two parallel paths and two cross paths. That is,
Fiber 18 connects the connection output port 24 ₁ and the connecting input port 28 _{1 1} and the connection output port 2
4 ₄ an optical fiber 18 ₄ for connecting the connecting input port 28 ₄ constitute a parallel path, connected output port 24 ₂
Optical fiber 1 for connecting the connecting input port 28 ₃ and
8 ₂ and the connection output port 24 ₃ and the connecting input port 28 ₂ and the optical fiber 18 ₃ connecting constitutes a crossing path. Such a relationship is established between the banyan optical switching units 16a ₁ and 16a ₂ of the input stage 12 and the output stage 14a.
Banyan optical switching units 16b ₁ , 16b
Same for all cases between ₂ . That is,
Any one banyan optical switching unit of the input stage 12 and all banyan optical switching units 16b ₁ , 16b _{2 of} the output stage 14 form a path bundle consisting of two parallel paths and two cross paths. Connected through.

Further, of the eight input ports of each banyan optical switching unit of the input stage 12, four input ports connected to different unit optical switches are used as input ports of the optical switching network 100. For example, for Banyan optical switching unit 16a _1, 4 pieces for using the input port 20 ₁ to 20 ₄ as an input port of the switching network 100, two Banyan optical switching unit 16a _1, consisting of 16a ₂ input stage 12 in total, eight of the input port 20 ₁ to 20 ₈
Are used as input ports of the optical switching network 100.

Further, among the eight output ports of the individual banyan optical switching units of the output stage 14, four output ports connected to different unit optical switches are used as output ports of the optical switching network 100. For example, for Banyan optical switching units 16b _1, 4 single output for use port 22 _{1-22 4} as an output port of the switching network 100, two Banyan optical switching units 16b _1, consisting 16b ₂ output stage 14 In total, eight output ports 22 _{1 to} 22 ₈
Are used as output ports of the optical switching network 100.

Therefore, the optical switching network 100 has 8
This is an optical switching network with eight inputs and eight outputs.

Due to the above configuration, each of the eight input and eight output banyan optical switching units of the input stage 12 has an apparent number of four from the input port side to the output port side of the optical switching network 100. (A unit optical switch of the corresponding portion is indicated by a white circle in FIG. 3) and a portion that operates as two 4-input / 4-output banyan optical switches. (In FIG. 3, the unit optical switches in the corresponding portions are indicated by hatching in circles.) Similarly, each of the eight inputs 8 of the output stage 14
The output banyan-type optical switching unit apparently operates as four 1-input 2-output branch optical switches from the output port side to the input port side of the optical switching network 100 (corresponding portions in FIG. 3). Are shown by white circles.) And a portion that operates as two 4-input / 4-output Banyan optical switches (in FIG. 3, the unit optical switches of the corresponding portions are hatched in the circles). Are shown as connected.) In other words, it is connected to a different unit optical switch among the eight input ports of the Banyan optical switching unit constituting the input stage 12 so as to have a portion that operates as four one-input two-output branch switches. The banyan-type optical switching unit constituting the input stage 12 has four input ports as input ports of the optical switching network 100 and has a portion that operates as two 4-input 4-output banyan-type optical switches. Eight output ports are used as output ports for connection with individual banyan optical switching units constituting the output stage 14. Similarly, among the eight output ports of the Banyan type optical switching unit constituting the output stage 14, they are connected to different unit optical switches so as to have a portion that operates as four one-input two-output branch switches. Four output ports are used as output ports of the optical switching network 100, and
The eight input ports of the banyan-type optical switching unit constituting the output stage 14 are divided into individual banyan-type optical switches constituting the input stage 12 so as to have a portion operating as a four-input four-output banyan-type optical switch. Used as an input port for connection to the switching unit.

In order to facilitate understanding of the optical switching network of the present invention, an optical switching network 100 shown in FIG.
Of the unit optical switches constituting the unit optical switch 26
₁ and positions of the 26 _2, the position of the unit optical switch 26 ₃ and 26 _4, replacing the positions of the unit optical switch 26 ₅ and 26 _7, and the unit optical switch 26 ₆ and 26 _8, further unit optical switch 26 ₉ to the position of the unit optical switch 26 _12, the unit optical switch 26 ₁₀ unit optical switch 26 ₉
The unit optical switch 26 ₁₄ to the unit optical switch 26
Move unit optical switch 26 ₁₁ to unit optical switch 2 to position ₁₁
6 ₁₃ to the position of the unit optical switch 26 ₁₃ to the position of the unit optical switch 26 _14, and, the configuration of an optical switching network 100 in the case of repositioning the unit optical switch 26 ₁₂ to the position of the unit optical switch 26 ₁₀ FIG. It is shown in FIG.

As can be understood from FIG. 4, any one path bundle, four output ports of the banyan optical switching unit of the input stage connected by the path bundle, and the banyan optical switching unit of the output stage. With 4
A total of four unit optical switches connected to the input ports, a total of eight waveguides connected to the four unit optical switches, a total of four unit optical switches connected to the eight waveguides, and The portion composed of a total of eight waveguides connected to the four unit optical switches operates as a non-blocking four-input four-output optical switch in a broad sense. That is, two 4 connected to any one path bundle
A portion composed of a four-input, four-output banyan optical switch (one for each of the input stage and the output stage) operates as a non-blocking, four-input, four-output optical switch in a broad sense. And this optical switching network 100
From the input port side to the output port side, apparently,
Portions operating as eight 1-input 2-output branch optical switches (in FIG. 4, the unit optical switches of the corresponding portions are indicated by white circles). Four broad non-blocking 4-input 4-outputs in part (FIG. 4 which operates as an optical switch 30 ₁ to 30 _4,
The unit optical switch of the corresponding portion is hatched in a circle. ) And eight portions operating as two-input one-output branch optical switches (in FIG. 4, the unit optical switches of the corresponding portions are indicated by white circles).

[0034] Thus, using the optical switching network 100, the output port 22 ₁ to the input port 20 ₁ to 20 ₈
When transmitting a signal light to 22 _8, in one input and two output branches optical switch of the input port side, to be output from the output port of the code 22 _{1-22 4} is outputted from the output port of the code 22 _{5-22 8} Or choose. In addition, 1 on the output port side
Either connect the branch optical switch inputs and two outputs and optical switch having four inputs and four outputs of the code 30 _1, choose whether to connect the optical switch 4 inputs and four outputs of the code 30 _2. Or code 3
0 ₃ 4 input 4 output optical switch
0 of ₄ of 4 inputs and four outputs for selecting whether to connect to the optical switch. Which input port is connected to which output port is determined by controlling a non-blocking type 4-input / 4-output optical switch in a broad sense. In this case, a switching algorithm of a unit optical switch constituting a 4-input / 4-output optical switch,
That is, if the switching order is specific, it is not blocked. Thus, if the four-input four-output optical switch operates as a broadly-defined non-blocking type optical switch, the optical switching network 100 also operates as a broadly-defined non-blocking type optical switching network.

Further, the crosstalk of the optical switching network 100 basically only occur in a broad non-closed 4-input 4-output optical switch 30 ₁ to 30 _4. To via four unit optical switch 26 the light for transmitting the optical switch 30 ₁ to 30 ₄ of the 4-input 4-output optical switching network 10
A crosstalk of 0 is only 6 dB worse than the unit optical switch.

When forming the optical switching network 100, first, a banyan optical switching unit is formed independently, and thereafter, a plurality of banyan optical switching units are used and connected as described above. Therefore, it is only necessary to form a banyan optical switching unit on the same substrate. Therefore, it is possible to reduce the adverse effect that the formation of the optical switching network becomes difficult because the length of the optical switching network becomes longer. When the optical switching network 100 is formed on the same substrate, the length of the optical switching network 100 is about the sum of the input stage 12 and the output stage 14, that is, the length of the banyan optical switching unit constituting the input stage 12. And the length of the banyan optical switching unit constituting the output stage 14. Since the length of the banyan optical switching network is originally short, it is considered that the length of the optical switching network 100 can be kept short even when two stages (input stage and output stage) are combined.

The optical switching network 100 has four path bundles each composed of two parallel paths and two cross paths, and has a completely non-blocking 8-input / 8-output type having 64 path bundles. The configuration is simpler than that of the tree type optical switching network.

3. Second Embodiment FIG. 5 is a diagram provided for describing an optical switching network according to a second embodiment. The switching network according to the second embodiment is a switching network in which N is set to 16. That is, FIG.
1A shows an optical switching network 200 having an input stage 12 and an output stage 14 configured by arranging four banyan optical switching units, and connecting the input stage 12 and the output stage 14. It is shown. However, FIG. 5A shows a path bundle including two parallel paths and two cross paths using an abbreviated view shown in FIG. 5B.

Each banyan-type optical switching unit is formed of a plurality of waveguides (including an input port and an output port) and a plurality of unit optical switches, and has 16 input ports and 16 output ports.
In this case, each banyan-type optical switching unit is formed on a different substrate 10. Note that in FIG. 5, the input of having input ports of Banyan optical switching unit 16a ₁ ~16a ₄ stage 12, input port 20 ₁ to 20 ₁₆ of 16 to be used as an input port of the optical switching network 200 only are shown, the output of having the output port of the Banyan optical switching units 16b ₁ ~16b ₄ stages 14, 16 output ports 2 combined is used as an output port of the optical switching network 200
Shows only 2 _{1-22 16.}

Further, the input Banyan optical switching unit 16a ₁ of the stage 12, and when focusing on Banyan optical switching units 16b ₁ of the output stage 14, input stage 12 Banyan optical switching unit 16a ₁ 16 pieces of having the Of the output ports, four connection output ports connected to two adjacent unit optical switches, and the banyan optical switching unit 16b _{1 of the} output stage 14
Out of the 16 input ports of the above, four connection input ports connected to two adjacent unit optical switches are connected via a path bundle consisting of two parallel paths and two cross paths. doing. Such a relationship, Banyan optical switching unit 16a ₁ of the input stage 12 ~16a ₄
And banyan optical switching unit 16 of output stage 14
It is the same for all cases between the b ₁ ~16b _4. That is, with any one of the Banyan switching unit of the input stage 12, a route bundle of all the Banyan switching unit 16b ₁ ~16b ₄ and the two parallel paths and two cross paths of the output stage 14 Connected through.

Of the 16 input ports of each banyan optical switching unit of the input stage 12,
Four input ports connected to different unit optical switches are used as input ports of the optical switching network 200. For example, for Banyan optical switching unit 16a _1, four input for use ports 20 ₁ to 20 ₄ as an input port of the switching network 200, the input stage consists of four Banyan optical switching unit 16a ₁ ~16a ₄ 12 overall, 16 of the input port 20 ₁ to 20
₁₆ is used as an input port of the optical switching network 200.

Further, of the 16 output ports of each banyan optical switching unit of the output stage 14,
Four output ports connected to different unit optical switches are used as output ports of the optical switching network 200. For example, for Banyan optical switching units 16b _1, four for using the output port 22 ₁ to 22 ₄ as an output port of the switching network 200, an output stage composed of four Banyan optical switching units 16b ₁ ~16b ₄ 14 overall, 16 output ports 20 ₁ to 22
₁₆ is used as an output port of the optical switching network 200.

Therefore, this optical switching network 200 has
This is an optical switching network having 6 inputs and 16 outputs.

With the above configuration, the optical switching network 200 can obtain the same effects as those of the optical switching network 100. However, the optical switching network 200 has a path bundle consisting of two parallel paths and two
The configuration is simpler than that of a completely non-blocking type 16-input / 16-output tree-type optical switching network having 256 path bundles.

It is clear that the present invention is not limited to the above first and second embodiments. For example,
In each of the embodiments described above, the predetermined input port and output port of the N-input N-output banyan optical switching unit are replaced with the input port, output port and input-stage optical switching unit and output-stage optical switching unit of the optical switching network. Is used as a connection input port and a connection output port for connecting to the device, but the input port, output port, connection input port, and connection output port are specified, and signals are sent from the input port to the output port. Only a path for transmitting light may be formed. That is, the same effect can be obtained even when unnecessary waveguides and unit optical switches are not formed.

In the first and second embodiments described above,
The case where N is 8 and 16 has been described.
The same effect can be obtained even when it is larger.

[0047]

As is apparent from the above description, according to the optical switching network of the present invention, N input ports and N output ports are formed from a plurality of waveguides and a plurality of unit optical switches. An input stage formed by arranging N / 4 banyan-type optical switching units having ports, a plurality of waveguides, and a plurality of unit optical switches;
An output stage in which N / 4 banyan-type optical switching units having N input ports and N output ports are arranged, and the input stage and the output stage are connected. Here, N is 2 ^a (a is an integer of 3 or more).

Each unit in the input stage has a portion which operates as four 1-input N / 4-output branch optical switches from the input port side to the output port side of each unit in the input stage. Thus, among the N input ports of the individual units in the input stage, four input ports connected to different unit optical switches are selected as input ports of the optical switching network. For this reason, each N-input N-output banyan optical switching unit in the input stage apparently branches four 1-input N / 4 outputs from the input port side to the output port side of the optical switching network. A part that operates as an optical switch and N / 4 4
It can be regarded as a configuration in which a part operating as an input four-output banyan optical switch is connected.

Similarly, each unit in the output stage has a portion operating as four 1-input N / 4-output branch optical switches from the output port side to the input port side of each unit in the output stage. From among the N output ports of the individual units in the output stage, four output ports connected to different unit optical switches are selected as output ports of the optical switching network. For this reason, each of the N-input N-output banyan optical switching units of the output stage apparently branches four 1-input N / 4 outputs from the output port side to the input port side of the optical switching network. A part that operates as an optical switch and N / 4 4
It can be regarded as a configuration in which a part operating as an input four-output banyan optical switch is connected.

Further, according to the optical switching network of the present invention, each of the N / 4 units in the input stage is connected to each of the N / 4 units in the output stage. Is connected to four output ports connected to two adjacent unit optical switches among N output ports of the unit of the input stage, and N input ports of the unit of the output stage. Among them, four input ports connected to two adjacent unit optical switches are connected via a path bundle composed of two parallel paths and two cross paths.

In this case, an arbitrary one path bundle, four output ports of the input stage Banyan optical switching unit connected by the path bundle, and four output ports of the output stage Banyan optical switching unit. A total of four unit optical switches connected to the input ports, a total of eight waveguides connected to the four unit optical switches, a total of four unit optical switches connected to the eight waveguides, and the four unit optical switches A portion composed of a total of eight waveguides connected to one unit optical switch operates as a non-blocking type 4-input / 4-output optical switch in a broad sense. That is, two 4-input 4-output banyan-type optical switches (one each for the input stage and the output stage) connected to any one path bundle.
Each is provided. ) Operates as a non-blocking four-input four-output optical switch in a broad sense.

With the above-described configuration, the optical switching network of the present invention apparently has N 1-input N / 4-output branch light from the input port side to the output port side of the optical switching network. The part that operates as a switch, N ²
It can be regarded as a configuration in which / 16 broadly defined non-blocking 4-input / 4-output optical switches and N operating N / 4-input / 1-output branch optical switches are connected. I can do it. If the four-input four-output optical switch operates as a non-blocking optical switch in a broad sense, the optical switching network also operates as a non-blocking optical switching network in a broad sense. The crosstalk of the optical switching network according to the present invention basically occurs only in a portion that operates as a non-blocking type 4-input / 4-output optical switch in a broad sense. Since the light transmitted through the four-input four-output optical switch passes through the four unit optical switches, the crosstalk of the optical switching network according to the present invention is only 6 dB worse than the unit optical switch.

When the optical switching network of the present invention is formed, first, a banyan-type optical switching unit is independently formed, and thereafter, a plurality of banyan-type optical switching units are connected as described above. Therefore, it is only necessary to form a banyan optical switching unit on the same substrate. Therefore, it is possible to reduce the adverse effect that the formation of the optical switching network becomes difficult because the length of the optical switching network becomes longer. Further, when the optical switching network of the present invention is formed on the same substrate, the length of the optical switching network is about the sum of the input stage and the output stage, that is, the length of the banyan optical switching unit constituting the input stage. , About the sum of the length of the banyan optical switching unit constituting the output stage. Since the length of the banyan optical switching network is originally short, even in the case of the optical switching network of the present invention in which the two stages (input stage and output stage) are combined, the length of the optical switching network can be suppressed to be short. it is conceivable that.

[0054] Also, the optical switching network N input N output of the present invention, the route bundles of parallel paths and two cross paths of the two N ² / and 16 have been, N ² pieces of route bundles Is simpler than that of a completely non-blocking N-input N-output tree-type optical switching network having

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining a basic configuration of an optical switching network.

FIG. 2 is a schematic diagram illustrating a configuration of a banyan-type optical switching unit.

FIG. 3 is a schematic diagram illustrating an optical switching network according to a first embodiment.

FIG. 4 is a diagram for explaining an optical switching network according to a first embodiment;

FIG. 5A is a schematic diagram for explaining an optical switching network according to a second embodiment, and FIG. 5B is a schematic diagram of a path bundle.

6A is a tree type, FIG. 6B is a crossbar type,
(C) is a Benes-type optical switching network, and (D) is a banyan-type optical switching network.

FIG. 7 is a curve diagram showing crosstalk characteristics of the optical switching network.

FIG. 8 is a curve diagram showing the length of an optical switching network.

[Explanation of symbols]

10: substrate 12: input stage 14: output stage 16a, 16b: banyan optical switching unit 16ax: front stage 16ay: rear stage 18: optical fiber 20: input port 22: output port 24, 24 _{1 to} 24 ₁₆ : output port 26 for connection : Unit optical switch 28 _{1 to} 28 ₁₆ : Input port for connection 30 ₁ to 30 ₄ : Optical switch with 4 inputs and 4 outputs 50, 100, 200: Optical switching network

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04Q 3/52-3/52 101 H04B 10/02 H04L 12/28

Claims (1)

(57) [Claims] When N is 2 ^a (a is an integer of 3 or more), N has N input ports and N output ports formed from a plurality of waveguides and a plurality of unit optical switches. N input units formed by arranging N / 4 banyan optical switching units (hereinafter, may be abbreviated as units), a plurality of waveguides, and a plurality of unit optical switches. A switching network comprising: an output stage configured by arranging N / 4 units each having an input port and N output ports, wherein the switching network connects between the input stage and the output stage. Each of the N / 4 units of the stage is connected to each of the N / 4 units of the output stage, and the connection between the units is determined by the N of the unit of the input stage.
Of the four output ports, four output ports connected to two adjacent unit optical switches and two of the N input ports of the unit at the output stage are connected to two adjacent unit optical switches. The four input ports are connected through a path bundle consisting of two parallel paths and two cross paths, wherein each unit of the input stage is connected to each of the input stages. N input units of each unit of the input stage so as to have a portion that operates as four 1-input N / 4-output branch optical switches from the input port side to the output port side of the unit. Among the ports, four input ports connected to different unit optical switches are selected and used as input ports of the optical switching network, and each unit of the output stage is an individual unit of the output stage. N output ports of each unit in the output stage so as to have a portion that operates as four 1-input N / 4-output branch optical switches from the output port side of the unit to the input port side. An optical switching network, wherein four output ports connected to different unit optical switches are selected as output ports of the optical switching network.